#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <unistd.h>
#include <fcntl.h>
#include <android/log.h>
#include <jni.h>

#include "bzip2/bzlib.c"
#include "bzip2/crctable.c"
#include "bzip2/compress.c"
#include "bzip2/decompress.c"
#include "bzip2/randtable.c"
#include "bzip2/blocksort.c"
#include "bzip2/huffman.c"

static off_t offtin(u_char *buf) {
    off_t y;

    y = buf[7] & 0x7F;
    y = y * 256;
    y += buf[6];
    y = y * 256;
    y += buf[5];
    y = y * 256;
    y += buf[4];
    y = y * 256;
    y += buf[3];
    y = y * 256;
    y += buf[2];
    y = y * 256;
    y += buf[1];
    y = y * 256;
    y += buf[0];

    if (buf[7] & 0x80)
        y = -y;

    return y;
}

int applypatch(int argc, char *argv[]) {
    FILE *f, *cpf, *dpf, *epf;
    BZFILE *cpfbz2, *dpfbz2, *epfbz2;
    int cbz2err, dbz2err, ebz2err;
    int fd;
    ssize_t oldsize, newsize;
    ssize_t bzctrllen, bzdatalen;
    u_char header[32], buf[8];
    u_char *old, *new;
    off_t oldpos, newpos;
    off_t ctrl[3];
    off_t lenread;
    off_t i;

    if (argc != 4)
        errx(1, "usage: %s oldfile newfile patchfile\n", argv[0]);

    /* Open patch file */
    if ((f = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);

    /*
     File format:
     0	8	"BSDIFF40"
     8	8	X
     16	8	Y
     24	8	sizeof(newfile)
     32	X	bzip2(control block)
     32+X	Y	bzip2(diff block)
     32+X+Y	???	bzip2(extra block)
     with control block a set of triples (x,y,z) meaning "add x bytes
     from oldfile to x bytes from the diff block; copy y bytes from the
     extra block; seek forwards in oldfile by z bytes".
     */

    /* Read header */
    if (fread(header, 1, 32, f) < 32) {
        if (feof(f))
            errx(1, "Corrupt patch\n");
        err(1, "fread(%s)", argv[3]);
    }

    /* Check for appropriate magic */
    if (memcmp(header, "BSDIFF40", 8) != 0)
        errx(1, "Corrupt patch\n");

    /* Read lengths from header */
    bzctrllen = offtin(header + 8);
    bzdatalen = offtin(header + 16);
    newsize = offtin(header + 24);
    if ((bzctrllen < 0) || (bzdatalen < 0) || (newsize < 0))
        errx(1, "Corrupt patch\n");

    /* Close patch file and re-open it via libbzip2 at the right places */
    if (fclose(f))
        err(1, "fclose(%s)", argv[3]);
    if ((cpf = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);
    if (fseeko(cpf, 32, SEEK_SET))
        err(1, "fseeko(%s, %lld)", argv[3], (long long) 32);
    if ((cpfbz2 = BZ2_bzReadOpen(&cbz2err, cpf, 0, 0, NULL, 0)) == NULL)
        errx(1, "BZ2_bzReadOpen, bz2err = %d", cbz2err);
    if ((dpf = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);
    if (fseeko(dpf, 32 + bzctrllen, SEEK_SET))
        err(1, "fseeko(%s, %lld)", argv[3], (long long) (32 + bzctrllen));
    if ((dpfbz2 = BZ2_bzReadOpen(&dbz2err, dpf, 0, 0, NULL, 0)) == NULL)
        errx(1, "BZ2_bzReadOpen, bz2err = %d", dbz2err);
    if ((epf = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);
    if (fseeko(epf, 32 + bzctrllen + bzdatalen, SEEK_SET))
        err(1, "fseeko(%s, %lld)", argv[3],
            (long long) (32 + bzctrllen + bzdatalen));
    if ((epfbz2 = BZ2_bzReadOpen(&ebz2err, epf, 0, 0, NULL, 0)) == NULL)
        errx(1, "BZ2_bzReadOpen, bz2err = %d", ebz2err);

    if (((fd = open(argv[1], O_RDONLY, 0)) < 0)
        || ((oldsize = lseek(fd, 0, SEEK_END)) == -1)
        || ((old = malloc(oldsize + 1)) == NULL)
        || (lseek(fd, 0, SEEK_SET) != 0)
        || (read(fd, old, oldsize) != oldsize) || (close(fd) == -1))
        err(1, "%s", argv[1]);
    if ((new = malloc(newsize + 1)) == NULL)
        err(1, NULL);

    oldpos = 0;
    newpos = 0;
    while (newpos < newsize) {
        /* Read control data */
        for (i = 0; i <= 2; i++) {
            lenread = BZ2_bzRead(&cbz2err, cpfbz2, buf, 8);
            if ((lenread < 8)
                || ((cbz2err != BZ_OK) && (cbz2err != BZ_STREAM_END)))
                errx(1, "Corrupt patch\n");
            ctrl[i] = offtin(buf);
        };

        /* Sanity-check */
        if (newpos + ctrl[0] > newsize)
            errx(1, "Corrupt patch\n");

        /* Read diff string */
        lenread = BZ2_bzRead(&dbz2err, dpfbz2, new + newpos, ctrl[0]);
        if ((lenread < ctrl[0])
            || ((dbz2err != BZ_OK) && (dbz2err != BZ_STREAM_END)))
            errx(1, "Corrupt patch\n");

        /* Add old data to diff string */
        for (i = 0; i < ctrl[0]; i++)
            if ((oldpos + i >= 0) && (oldpos + i < oldsize))
                new[newpos + i] += old[oldpos + i];

        /* Adjust pointers */
        newpos += ctrl[0];
        oldpos += ctrl[0];

        /* Sanity-check */
        if (newpos + ctrl[1] > newsize)
            errx(1, "Corrupt patch\n");

        /* Read extra string */
        lenread = BZ2_bzRead(&ebz2err, epfbz2, new + newpos, ctrl[1]);
        if ((lenread < ctrl[1])
            || ((ebz2err != BZ_OK) && (ebz2err != BZ_STREAM_END)))
            errx(1, "Corrupt patch\n");

        /* Adjust pointers */
        newpos += ctrl[1];
        oldpos += ctrl[2];
    };

    /* Clean up the bzip2 reads */
    BZ2_bzReadClose(&cbz2err, cpfbz2);
    BZ2_bzReadClose(&dbz2err, dpfbz2);
    BZ2_bzReadClose(&ebz2err, epfbz2);
    if (fclose(cpf) || fclose(dpf) || fclose(epf))
        err(1, "fclose(%s)", argv[3]);

    /* Write the new file */
    if (((fd = open(argv[2], O_CREAT | O_TRUNC | O_WRONLY, 0666)) < 0)
        || (write(fd, new, newsize) != newsize) || (close(fd) == -1))
        err(1, "%s", argv[2]);

    free(new);
    free(old);

    return 0;
}

/*
 * Class:     com_dhy_bspatch_PatchUtils
 * Method:    patch
 * Signature: (Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)I
 */
JNIEXPORT jint JNICALL
Java_com_dhy_bspatch_PatchUtils_patch(JNIEnv *env, jclass clazz, jstring old, jstring new, jstring patch) {

    char *ch[4];
    ch[0] = "bspatch";
    ch[1] = (char *) ((*env)->GetStringUTFChars(env, old, 0));
    ch[2] = (char *) ((*env)->GetStringUTFChars(env, new, 0));
    ch[3] = (char *) ((*env)->GetStringUTFChars(env, patch, 0));

    __android_log_print(ANDROID_LOG_INFO, "ApkPatchLibrary", "old = %s ", ch[1]);
    __android_log_print(ANDROID_LOG_INFO, "ApkPatchLibrary", "new = %s ", ch[2]);
    __android_log_print(ANDROID_LOG_INFO, "ApkPatchLibrary", "patch = %s ", ch[3]);

    int ret = applypatch(4, ch);

    __android_log_print(ANDROID_LOG_INFO, "ApkPatchLibrary", "applypatch result = %d ", ret);

    (*env)->ReleaseStringUTFChars(env, old, ch[1]);
    (*env)->ReleaseStringUTFChars(env, new, ch[2]);
    (*env)->ReleaseStringUTFChars(env, patch, ch[3]);

    return ret;
}